By our reformed-Macleanian model, then, the r-complex will be understood additionally to be allowed to include proto-limbic structures. The r-complex, including those additional structures, will continue to be understood to be the physical seat of the instincts such as they manifest in the human brain. It will continue to be understood that, the human brain’s r-complex, removed of all later evolutionary brain layers, would revert to all of the behavioral traits of an instinct-only brain on a par with the reptile behavior.
Immediately beyond the r-complex, in the evolutionary layering of the human brain, we find the paleo-mammalian brain. This layer begins with the limbic system (versus a proto-limbic system). The limbic system modifies desire from the level of instinct to the level of emotion. As it develops it also progressively transfers sensory dominance from the olfactory to the visual sense. The olfactory sense, in the human brain, remains almost entirely wired into the r-complex. The more developed the paleo-mammalian brain, the more dominant becomes the input of the visual sense into brain processing.
The same may be said, to a lesser degree, about the aural sense. The more developed the paleo-mammalian brain, the more dominant becomes the input of the aural sense into brain processing.
These facts are exhibited in the structure of the paleo-mammalian portion of the human brain and are in general paralleled in the evolutionary tree of mammals themselves as we understand it via the study of living mammals representative of various evolutionary stages. They reveal to us an absolutely certain fact of Consciousness. Sensory data of a high degree of discrimination and acuity precedes the development of Consciousness. The seat of all sensory reception resides, regardless of the degree of evolutionary progress or Consciousness, in not-conscious portions of the human brain. Consciousness-qua-Consciousness receives no direct, and, therefore, no un-mediated, sensory input. The Consciousness can only be profoundly bereft of sensation in all immediate senses.
Even as early as the instinct-only brain, immediate sensory input must be mediated in a wide variety of ways in order for the brain to accomplish its functions. Certain scents must betoken a female in heat, must promise associated neurological reward. Certain sights must betoken that a competitor for the female is much larger, and, therefore, the female must be foregone. Certain sounds must betoken that a challenge to or for territory is at hand. These may properly be described as “proto-meanings”. Such proto-meanings can only be arrived at by mediation of the sensory inputs as they are passed along to the primitive processing areas of the instinct-only brain.
We begin now to be able to list some features of Consciousness, although these features are largely negative:
1. All forms of life may have a sense of self corresponding to their composition and circumstances. Therefore, conscious forms of life can not be discriminated from other